The present invention relates generally to rotary machine and more specifically to a pump or turbine rotary machine.
Centrifugal pumps are widely used due to their simplicity of design and generally acceptable efficiency. An inherent problem in many industrial applications is that the pressure generated by a basic centrifugal pump is inadequate. In order to obtain the desired pressure in such cases, many impellers must be used, which is called multi-staging. Multi-staging results in a very complex and expensive rotor and casing. Another approach to generating the desired pressure is to a single impeller at very high speed. High-speed operation requires expensive shaft speed step-up equipment such as gear boxes or belt drives. Moreover such pump are noisy and generally unreliable.